Biliary acute pancreatitis: A review

Anatomical and functional characterization of a duodeno-pancreatic neural reflex that can induce acute pancreatitis

Neural cross talk between visceral organs may play a role in mediating inflammation and pain remote from the site of the insult. We hypothesized such a cross talk exists between the duodenum and pancreas, and further it induces pancreatitis in response to intraduodenal toxins. A dichotomous spinal innervation serving both the duodenum and pancreas was examined, and splanchnic nerve responses to mechanical stimulation of these organs were detected. This pathway was then excited on the duodenal side by exposure to ethanol followed by luminal mustard oil to activate transient receptor potential subfamily A, member 1 (TRPA1). Ninety minutes later, pancreatic inflammation was examined. Ablation of duodenal afferents by resiniferatoxin (RTX) or blocking TRPA1 by Chembridge (CHEM)-5861528 was used to further investigate the duodeno-pancreatic neural reflex via TRPA1. ~40% of dorsal root ganglia (DRG) from the spinal cord originated from both duodenum and pancreas via dichotomous peripheral branches; ~50% splanchnic nerve single units responded to mechanical stimulation of both organs. Ethanol sensitized TRPA1 currents in cultured DRG neurons. Pancreatic edema and myeloperoxidase activity significantly increased after intraduodenal ethanol followed by mustard oil (but not capsaicin) but significantly decreased after ablation of duodenal afferents by using RTX or blocking TRPA1 by CHEM-5861528. We found the existence of a neural cross talk between the duodenum and pancreas that can promote acute pancreatitis in response to intraduodenal chemicals. It also proves a previously unexamined mechanism by which alcohol can induce pancreatitis, which is novel both in terms of the site (duodenum), process (neurogenic), and receptor (TRPA1).

Recent insights into the cellular mechanisms of acute pancreatitis

In acute pancreatitis, initiating cellular events causing acinar cell injury includes co-localization of zymogens with lysosomal hydrolases, leading to premature enzyme activation and pathological exocytosis of zymogens into the interstitial space. This is followed by processes that accentuate cell injury; triggering acute inflammatory mediators, intensifying oxidative stress, compromising the microcirculation and activating a neurogenic feedback. Such localized events then progress to a systemic inflammatory response leading to multiorgan dysfunction syndrome with resulting high morbidity and mortality. The present review discusses some of the most recent insights into each of these cellular processes postulated to cause or propagate the process of acute pancreatitis, and also the role of alcohol and genetics.

Relaxin prevents the development of severe acute pancreatitis

AIM: To investigate the severity of acute pancreatitis (AP) is associated to the intensity of leukocyte activation, inflammatory up-regulation and microcirculatory disruption associated to ischemia-reperfusion injury. Microvascular integrity and inhibition of pro-inflammatory mediators are key-factors in the evolution of AP. Relaxin is an insulin-like hormone that has been attributed vasorelaxant properties via the nitric oxide pathway while behaving as a glucocorticoid receptor agonist.

METHODS: AP was induced by the bilio-pancreatic duct-outlet-exclusion closed-duodenal-loops model. Treatment with relaxin was done at different time-points. Nitric oxide synthase inhibition by L-NAME and glucocorticoid receptor (GR) blockage by mifepristone was considered. AP severity was assessed by biochemical and histopathological analyses.

RESULTS: Treatment with relaxin reduced serum amylase, lipase, C-reactive protein, IL-6, IL-10, hsp72, LDH and 8-isoprostane as well as pancreatic and lung myeloperoxidase. Acinar and fat necrosis, hemorrhage and neutrophil infiltrate were also decreased. ATP depletion and ADP/ATP ratio were reduced while caspases 2-3-8 and 9 activities were increased. L-NAME and mifepristone decreased the efficiency of relaxin.

CONCLUSION: Relaxin resulted beneficial in the treatment of AP combining the properties of a GR agonist while preserving the microcirculation and favoring apoptosis over necrosis.

Experimental model of acute pancreatitis in Wistar rat: glucocorticoid treatment profile

Severe acute pancreatitis may be triggered by an extrapancreatic insult at the peri-Vaterian duodenum such as that occurring in the short-term, 20 min closed duodenal loop model in Wistar rat, which mimics biliary acute pancreatitis or that following endoscopy. Glucocorticoids are immunological modulators whose therapeutic value is worth investigating. Wistar male rats were used under standardized conditions. Acute pancreatitis was induced by instillation of a 7% sodium tauraocholate solution with 5 drops of methylene blue to monitor absence of duodenal bilio pancreatic reflux into the peri-Vaterian duodenum for 20 min. Detection of biliopancreatic reflux with methylene blue was an exclusion criterion. Different doses and times of administration of subcutaneous hydrocortisone were evaluated. Biochemical assays were carried out in blood samples and pancreatic and lung tissue, while histpathological studies were done in the pancreas, lung liver, duodenum, spleen, kidneys, suprarenal glands, and stomach. Animals subjected to the experimental model developed severe acute pancreatitis. According to the dose and time of administration, hydrocortisone therapy was effective and beneficial at a dose of 4 mg/kg give 30 min before inducing acute pancreatitis. It was ineffective when doses were <4 mg/kg and given before sodium taurocholate harmful when the dose was >4 mg/kg and given either before or after. Thus, the proposed model is valid and useful to study the initiation mechanism of acute pancreatitis caused extrapancreatically while its amelioration by glucocorticoid is related the dose and time factor to achieve therapeutical results.

Experimental model of acute pancreatitis in Wistar rat: glucocorticoid treatment profile

Severe acute pancreatitis may be triggered by an extrapancreatic insult at the peri-Vaterian duodenum such as that occurring in the short-term, 20 min closed duodenal loop model in Wistar rat, which mimics biliary acute pancreatitis or that following endoscopy. Glucocorticoids are immunological modulators whose therapeutic value is worth investigating. Wistar male rats were used under standardized conditions. Acute pancreatitis was induced by instillation of a 7% sodium tauraocholate solution with 5 drops of methylene blue to monitor absence of duodenal bilio pancreatic reflux into the peri-Vaterian duodenum for 20 min. Detection of biliopancreatic reflux with methylene blue was an exclusion criterion. Different doses and times of administration of subcutaneous hydrocortisone were evaluated. Biochemical assays were carried out in blood samples and pancreatic and lung tissue, while histpathological studies were done in the pancreas, lung liver, duodenum, spleen, kidneys, suprarenal glands, and stomach. Animals subjected to the experimental model developed severe acute pancreatitis. According to the dose and time of administration, hydrocortisone therapy was effective and beneficial at a dose of 4 mg/kg give 30 min before inducing acute pancreatitis. It was ineffective when doses were <4 mg/kg and given before sodium taurocholate harmful when the dose was >4 mg/kg and given either before or after. Thus, the proposed model is valid and useful to study the initiation mechanism of acute pancreatitis caused extrapancreatically while its amelioration by glucocorticoid is related the dose and time factor to achieve therapeutical results.

A mouse model of severe acute pancreatitis induced with caerulein and lipopolysaccharide

AIM: To establish a non-traumatic, easy to induce and reproducible mouse model of severe acute pancreatitis (SAP) induced with caerulein and lipopolyasccharide (LPS).

METHODS: Thirty-two healthy mature NIH female mice were selected and divided at random into four groups (each of 8 mice), i.e., the control group (NS group), the caerulein group (Cn group), the lipopolysaccharide group (LPS group), and the caerulein+LPS group (Cn + LPS group). Mice were injected intraperitoneally with caerulein only, or LPS only, and caerulein and LPS in combination. All the animals were then killed by neck dislocation three hours after the last intraperitoneal injection. The pancreas and exo-pancreatic organs were then carefully removed for microscopic examination. And the pancreatic acinus was further observed under transmission electron microscope (TEM). Pancreatic weight, serum amylase, serum nitric oxide (NO) concentration, superoxide dismutase (SOD) and malondialdehyde (MDA) concentration of the pancreas were assayed respectively.

RESULTS: (1) NS animals displayed normal pancreatic structure both in the exocrine and endocrine. In the LPS group, the pancreas was slightly edematous, with the infiltration of a few inflammatory cells and the necrosis of the adjacent fat tissues. All the animals of the Cn group showed distinct signs of a mild edematous pancreatitis characterized by interstitial edema, infiltration of neutrophil and mononuclear cells, but without obvious parenchyma necrosis and hemorrhage. In contrast, the Cn + LPS group showed more diffuse focal areas of nonviable pancreatic and hemorrhage as well as systemic organ dysfunction. According to Schmidt’s criteria, the pancreatic histologic score showed that there existed significant difference in the Cn + LPS group in the interstitial edema, inflammatory infiltration, parenchyma necrosis and parenchyma homorrhage in comparison with those of the Cn group, LPS group and NS group (P < 0.01 or P < 0.05). (2) The ultrasturcture of acinar cells was seriously damaged in the Cn + LPS group. Chromatin margination of nuclei was present, the number and volume of vacuoles greatly increased. Zymogen granules (ZGs) were greatly decreased in number and endoplasmic reticulum exhibited whorls. The swollen mitochondria appeared, the crista of which was decreased in number or disappeared. (3) Pancreatic weight and serum amylase levels in the Cn +LPS was significantly higher than those of the NS group and the LPS group respectively (P < 0.01 or P < 0.05). However, the pancreatic wet weight and serum amylase concentration showed no significant difference between the Cn + LPS group and the Cn group. (4) NO concentration in the Cn + LPS group was significantly higher than that of NS group, LPS group and Cn group(P < 0.05 or P < 0.01). 5) The SOD and MDA concentration of the pancreas in the Cn + LPS group were significantly higher than those of NS, LPS and Cn groups (P < 0.05 or P < 0.01).

CONCLUSION: The mouse model of severe acute pancreatitis could be induced with caerulein and LPS, which could be non-traumatic and easy to induce, reproducible with the same pathological characteristics as those of SAP in human, and could be used in the research on the mechanism of human SAP.

Role of NF-κB in multiple organ dysfunction during acute obstructive cholangitis

AIM: To elucidate the role of NF-κB activation in the development of multiple organ dysfunction (MOD) during acute obstructive cholangitis (AOC) in rats.

METHODS: Forty-two Wistar rats were divided into three groups: the AOC group, the group of bile duct ligation (BDL group), and the sham operation group (SO group). All the animals in the three groups were killed in the 6th and 48th hour after operation. Morphological changes of vital organs were observed under light and electron microscopy. NF-κB activation was determined with Electrophoretic Mobility Shift Assay (EMSA). Arterial blood gas analyses and the serum levels of lactate dehydrogenase (LDH), alanine aminotransferase (ALT), blood urea nitrogen (BUN) and creatinine were performed. The concentrations of TNF-α and IL-6 in plasma were also measured.

RESULTS: The significant changes of histology and ultrastructure of vital organs were observed in AOC group. By contrast, in BDL group, all the features of organs damage were greatly reduced. Expression of NF-κB activation in various tissues increased in AOC group when compared to other two groups. At 6 h, the arterial pH in three groups was 7.52 ± 0.01, 7.46 ± 0.02, and 7.45 ± 0.02, and the blood pCO₂ was 33.9 ± 0.95 mmHg, 38.1 ± 0.89 mmHg, 38.9 ± 0.94 mmHg, there was difference in three groups (P < 0.05). At 48 h, the blood pHvalues in three groups was 7.33 ± 0.07, 7.67 ± 0.04, and 7.46 ± 0.03, and blood HCO₃^- was 20.1 ± 1.29 mmol·L^-1, 26.7 ± 1.45 mmol·L^-1 and 27.4 ± 0.35 mmol·L^-1, there was also difference in three groups (P < 0.05). In AOC group, Levels of LDH, ALT, BUN and creatinine were 16359.9 ± 2278.8 nkat·L^-1, 5796.2 ± 941.9 nkat·L^-1, 55.7 ± 15.3 mg/dl, and 0.72 ± 0.06 mg/dl, which were higher than in SO group (3739.1 ± 570.1 nkat·L^-1, 288.4 ± 71.7 nkat·L^-1, 12.5 ± 2.14 mg/dl, and 0.47 ± 0.03 mg/dl) (P < 0.05). Levels of plasma TNF-α and IL-6 in AOC at 48 h were 429 ± 56.62 ng·L^-1 and 562 ± 57 ng·L^-1, which increased greatly when compared to BDL group (139 ± 16 ng·L^-1, 227 ± 43 ng·L^-1) and SO group (74 ± 10 ng·L^-1, 113 ± 19 ng·L^-1) (P < 0.05).

CONCLUSION: The pathological damages and the NF-κB activation of many vital organs exised during AOC. These findings have an important implication for the role of NF-κB activation in MOD during AOC.

Pancreatic microcirculatory impairment in experimental acute pancreatitis in rats

AIM: To study the feature of pancreatic microcirculatory impairment, especially the initial changes, in caerulein-induced experimental acute pancreatitis (AP).

METHODS: The pancreatic microcirculation of caerulein-induced AP model was studied by intravital fluorescence microscopy with FITC-labeled erythrocytes (FITC-RBC), scanning electron microscopy of vascular corrosion casts, and light microscopy of Chinese ink-injected/cleared tissues.

RESULTS: Animals in caerulein-treated group showed hyperamylemia (× 2), pancreatic oedema, infiltration of inflammatory cells in pancreas. Constrictions of intralobular arteriolar sphincters, presence of vacuoles in all layers of sphincter, and gross irregularity in capillary network of acini were found in the AP specimens. The decrease of pancreatic capillary blood flow (0.34 ± 0.10 nL·min^-1vs 0.91 ± 0.06 nL·min^-1 of control, P < 0.001), reduction of functional capillary density (277 ± 13 cm^-1vs 349 ± 8 cm^-1 of control, P < 0.001), and irregular intermittent perfusion were observed in caerulein-induced groups.

CONCLUSION: Impairment and constriction of pancreatic intralobular arteriolar sphincter are the initial microcirculatory lesions in the early phase of acute pancreatitis, and play a key role in the pancreatic ischaemia and pancreatic microvascular failure in acute pancreatitis.

Early diagnosis and treatment of severe acute cholangitis

AIM: To investigate the diagnostic standard for early identification of severe acute cholangitis in order to lower the incidence of morbidity and mortality rate.

METHODS: A diagnostic standard was proposed in this study as follows: documented biliary duct obstruction by ultrasound or computerized tomography or other imaging tools with the manifestation of systemic inflammatory response syndrome (SIRS). The surgical procedures included emergency common bile duct exploration with T tube insertion or cholecystostomy with secondary common bile duct exploration. And incidence of postoperative multiple organ dysfunction syndrome (MODS), duration of systemic inflammatory response and hospital mortality were analyzed.

RESULTS: Fourty-three patients conforming to the diagnostic standard described above were employed in this study. 1 patient was admitted in acutely ill condition and complicated with acute relapse of chronic bronchitis, cholecystostomy procedure was performed but the patient was complicated with postoperative acute lung injury which was treated by assisted mechanical ventilation for 5 d; 2 wk later, two-stage common bile duct Exploration and T tube insertion were performed. The remaining 42 patients underwent primary common bile duct exploration and T tube insertion, 1 developed acute lung injury and recovered 3 d later, 2 patients developed acute renal dysfunction, 1 of which recovered 2 d later and the other died on d 4. For all patients, the postoperative systemic inflammatory response persisted for 2 to 8 d with median of 3 d.

CONCLUSION: Early diagnosis of severe acute cholangitis can be made using this diagnostic standard, further development of systemic inflammatory response could be prevented and incidence of MODS as well as hospital mortality decreased.